Igneous Rock (Volcanic Glass)

Pumice

Vesicular Felsic Extrusive Igneous Rock

Pumice

Highly vesicular volcanic glass, typically rhyolitic to andesitic composition; mainly silicate glass with feldspar, quartz, and minor pyroxene/amphibole.

Polished banded obsidian

Volcanic glass, predominantly SiO₂; likely banded or mahogany obsidian

Pumice

Pumice (a highly vesicular volcanic glass)

Snowflake Obsidian

Volcanic glass containing Spherulitic inclusions (SiO2 + impurities)

Orbicular rhyolite (likely)

Rhyolite, a silica-rich volcanic rock; commonly quartz, alkali feldspar, plagioclase, and iron-rich alteration minerals

Quartz Veined Diorite or Basalt

Crystalline Silicon Dioxide (Quartz) in Mafic Igneous Host (Basalt/Diorite)

Red Scoria

Scoria (Vesicular Basalt/Andesite)

Apache Tear (Obsidian)

Hydrated volcanic glass (SiO2 with inclusions)

Pumice

Vesicular volcanic glass (primarily SiO2)

Pumice

Vesicular Rhyolite (Amorphous glass)

Pumice

Pumice (a highly vesicular volcanic glass)

Red Agate

Chalcedony (SiO2)

Weathered vesicular volcanic rock (likely scoria or vesicular basalt)

Vesicular basalt/scoria; primarily plagioclase, pyroxene, olivine, and volcanic glass

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Vesicular basalt (likely scoriaceous basalt)

Mafic volcanic rock, chiefly plagioclase, pyroxene, and olivine; commonly iron-rich volcanic glass

Snowflake Obsidian

Volcanic glass containing Spherulites (SiO2)

Basalt

Mafic Igneous Rock

Basalt

Basalt

Milky Quartz with Chlorite/Mica inclusions

Silicon Dioxide (SiO2) with inclusions

Basalt

Basalt

Tumbled basalt

Basalt; fine-grained mafic volcanic rock, chiefly plagioclase and pyroxene with possible olivine and magnetite

Scoria (vesicular volcanic rock)

Scoria, typically basaltic or andesitic volcanic material

Black volcanic rock, possibly basalt or obsidian

Likely basalt (fine-grained mafic silicate rock); obsidian is a possible alternative

Pumice

Pumice (Vesicular Rhyolite/Dacite)

Weathered iron-rich volcanic rock

Likely basaltic andesite or altered basalt; precise identification requires testing

Weathered vesicular volcanic rock, likely scoria

Scoria (vesicular basaltic-andesite), compositionally dominated by plagioclase, pyroxene, and iron-rich glass

Obsidian (Polished)

Obsidian (Volcanic glass, primarily SiO2)

Pumice

Pumice (a highly vesicular volcanic glass)

Pumice

Pumice (Silicic volcanic glass with vesicular structure)

Polished black stone pendant, likely obsidian

Volcanic glass; primarily silica-rich rhyolitic glass (SiO₂), if obsidian

Vesicular basalt (likely scoria)

Basaltic volcanic rock; chiefly plagioclase, pyroxene, and olivine, with possible volcanic glass

Vesicular volcanic rock, likely pumice or scoria

Pumice (highly vesicular rhyolitic–andesitic volcanic glass) or scoria (vesicular basaltic–andesitic rock)

Pumice

Pumice (a highly vesicular volcanic glass)

Pumice

Pumice (Vesicular Felsic Igneous Rock)

Basalt

Extrusive Igneous Rock

Pumice

Pumice (volcanic glass with vesicular texture)

Pumice

Pumice (Highly vesicular volcanic glass)

Scoria (vesicular volcanic rock)

Basaltic scoria; chiefly plagioclase, pyroxene, olivine, and iron-rich volcanic glass

Weathered basalt or volcanic rock

Likely vesicular basalt; composition dominated by plagioclase and pyroxene, with possible iron-oxide alteration

Basalt

Basalt (Aphanitic Mafic Volcanic)

Vesicular basalt (probable scoriaceous basalt)

Basalt; chiefly plagioclase, clinopyroxene, and iron-titanium oxides, with possible olivine